Difficult question to answer. You see, the common name "Malaysian Sword" is commonly applied to a number of different plants, most of which are not true aquatics anyway.
Several species of Spathiphyllum are sold as "Malaysian Sword". This is very much a terrestrial plant and will rot away in a couple of months under water.
Aglaonema simplex is another bog plant which does much better under water than the above. It grows very slowly from a rhizome and looks vastly more like an Anubias species then a true sword. If you can get it, it is really very tough, and although I can't say for certain, it would not suprise me if it took a little salt.
Another possibility is ordinary Java Fern, which is also sold as "Malaysian Sword". This is an almost bullet proof plant which will definitely take some salt.
No easy yes/no answer I'm afraid. If you have some, try it. If you have a picture, post it.